rebuilt twin smoking

M

-Max-

Active Member
Hey guys, I Just rebuild my motor on my 70 cb175 a couple days ago, new piston rings seals and gaskets. Got the motor running and the left cylinder is blow a ton of white smoke. The smoke does have a fuel like smell and the plugs look normal. Any ideas on what might be up? All the searching ive done points to a bad head gasket but The one I have on is brand new. Any ways any help would be much appreciated. Thanks
Max
 
Im not sure what bike it is but did you line up the rings to face 120 degrees apart? Are there 2 rings and an oil seal? Is it a 2 stroke? It's normal if it's a 2 stroke. Are you talking about your twin sister who just had her titties rebuilt? DETAILS MAN .................. DETAILS.
 
Duh kinda spaces on that shit....... 1970 cb175. Rings were spaced prior to being put into the head. Tapets were also set.
 
I did use oil when I put rings back in, put some on the inside of the cylinder sleeves and on the piston its self. White smoke is coming out of the left cylinder exhaust only, breather appears fine, and smokes does smell a bit like oil. Also pulled the left cylinder plug and it looks a little wet and smells like fuel.
 
I also noticed that at idle there is very little smoke but when I rev it a lot of smoke pours out that pipe.
 
Sounds like rings fitted upside down or an oval bore or worn valve guides. What has been done to the motor so far? Ours smoke a little even with CB200 late model guides and seals.

Did you replace the valve guide oil seals?
 
Sorry, man. Still not correct. Unburned fuel is vaporous and has no color.

The only thing that causes white smoke is oil or coolant. And coolant isn't an issue on this bike.
 
teazer said:
Sounds like rings fitted upside down or an oval bore or worn valve guides. What has been done to the motor so far? Ours smoke a little even with CB200 late model guides and seals.

Did you replace the valve guide oil seals?
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No I didnt replace the valve guide seals. All that was done to the engine so far is Gaskets and seals changed, I cleaned the carbon off the head, valves, and pistons and changed the piston rings. Compression last I checked seemed a little low 120 psi.
 
Oil is usually blue smoke. Black is most unusual. White is water vapor - usually from a leaky head gasket sucking water in from the radiator but that doesn't apply here.

120PSI is not too bad on those motors. 140 would be nicer though. The rings may not have sealed or one or more are upside down. Try a leak down test and listen for air leaks. You should hear it hissing past the pistons or out of the ports. That will help you to work out what to do next.
 
Thanks man, Im thinking it might be a ring up side down, thought I put the in right side up but I could have botched one up. The two top rings had writing on them and the oil ring did not. Do you think the oil ring being upside down would have much to do with?
 
blue oil smoke has always been my experience. only see black smoke on a really rich running diesel engine. White smoke from headgasket leaks on liquid cooled engines. I've had a cylinder go dead on my bike before and limped it home. put a new plug in it and it puffed white untill it started firing again. *shrugs*
 
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